16-66 errors can be caused by the Sling app being unable to connect to your AirTV device.
Try the steps below to resolve the error:
Check that the AirTV device is plugged in and powered on - the indicator light on the front of the device should be green. A direct connection to a power outlet is preferred over a power strip.
Make sure the AirTV device is connected to the internet and that your internet connection is active. Either the WiFi or Ethernet indicator light should be on.
Check your firewall/NAT settings to ensure the device is not being blocked. Note: Customers using firewalls may be required to enable port forwarding. The TCP port is 5401. It is the standard SBSDK port. If the MAC address, the WiFi (active MAC) is found in the app, in the settings, and the Ethernet MAC is on the label.
If you're still receiving this error after attempting the steps above, please connect with AirTV at 866-974-1354.